12 volts or 14 volts ??

[mont]

Recently read part of the latest marine electrical bible.

There is a section on the actual voltage for marine '12v' use.

Theory is that actually a 12v system / batteries are nominally called that but you should be looking for about 14v in the batteries normally as follows.
Typical Marine batteries are effectively flat at about 10.5 volts and therefore if your batteries are normally sat at 12 - 12.5 v fully charged it only gives about 2 volts useage. After a bit of voltage drop in the system it dont leave much left.
Volvo alternators (like mine) are rated to 14v output which after passing through cable and those dreaded old fashioned split charging diodes gives about 12.75v at the batteries.

So theory goes :-
1. Get rid of diodes and let alternators (when under power) directly charge batts to 13.5 v plus
2. Change diodes to new 'smart' voltage regulators to remove voltage drop of about 1v. They seem to be rated at 14v so will allow full charge.
3. Get rid of old type shore power / charger and get a new one that will rate to 14v so starting at full charge.

So anyone got experiences to share on upgrading / increasing battery charge.

Surely most instruments are rated / happy with the bit extra as most are fuse protected which relates to the amps and if my memory serves the higher the voltage the lower the amperage ?

My batteries fully charged are at 12.75v with a drop of about 0.5 volts at the end on the loom on instruments etc. Is your system similar.

Comments / discussion welcomed........

 

[Carols]

I think it's the amp's that are more important than the volts, you can however get a Sterling alternator charging unit that will charge you batteries @ 13.8 volts when running.
Also on mains power you can get a Sterling unit which has a 5 stage charging system.

 

[pissativlypossed]

I can confirm that, I have just replaced a Christec charger which gave up the ghost after 3 years, with a Sterling power digital one. The old one would only give 13.5v the new one charges to 14.7v. I bought the 50amp model with a remote controller that monitors the charge in domestic and engine battery banks and auxillary batteries for Thruster and Anchor windlass.
Sterling also supply an advanced alternator regulator that does exactly as you say. They have a very informative website that is worth looking at. http://www.sterling-power.com/

 

[Boathook]

My batteries when fully charged seem to be around 12.5 volt and 14 volts during charge. With regards to wiring I use the biggest possible, within reason. This is around 6mm square conductor, the biggest for the yellow crimp terminals. Whether crimps should be used has been discussed elsewhere in various earlier threads.

 

[jcmmarine]

Unfortunatly phisics, technology, chemistry, and nature dictate and restricts battery capabilities.
There are lots of basic books on batteries and boat electrics, check the RYA web site.

 

[ms1]

I dumped the split charge diode as it sucked out about one volt out of the charge. Lead acid Batteries need a good charge at 14.6v dropping back to about 13.5ish .
I recommend Sterling charger, have one myself , you can get them from internet retailer like JGTECH. Your 20 year old battery charger out of the back of the garage wont do the biz.
Always keep battery fluid level checked and topped up.